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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 1 November 2012 by dana1981

Hurricane Sandy was an unprecedented storm in modern times, arriving late in the hurricane season, making landfall abnormally far to the north on the US east coast, with an exceptionally low pressure, and a record-breaking storm surge. The hurricane also had among the most kinetic energy of all tropical cyclones on record at 222 trillion Joules (the equivalent of 3.5 Little Boy Hiroshima atomic bombs) - more energy than Category 5 hurricanes like Katrina despite Sandy just being Category 1, because Sandy was spread over a much larger area.

Given the unprecedented nature of this event, many people are asking whether it was caused by or its impacts amplified by global warming, and many others are of course trying to deny any hurricane-climate links. There is actually a fairly simple answer to this question: human-caused climate change amplified the hurricane's impacts.

Higher Sea Levels Cause Bigger Storm Surges

One reason we can draw this conclusion is that as Michael Mann noted, sea levels around the New York area are now close to 1 foot higher than they were a century ago. For example, Figure 1 shows the annual mean sea level rise since 1900 for Battery Park, New York from tide gauge data.

While Battery Park represents just one tide gauge, there are many other tide gauges in the region which tell a very similar story, as you can see at the PSMSL site. And of course we know that the global sea level rise (approximately 0.6 feet since 1900, on average) is predominantly caused by melting land ice and the thermal expansion of the oceans. As Church et al. (2011) found, approximately 40% of the average global sea level rise since 1972 is due to thermal expansion, and approximately 60% due to land ice melting (Figure 2), both of which in turn are predominantly driven by human-caused global warming.

Figure 2: The global sea level budget from 1961 to 2008. (a) The observed sea level using coastal and island tide gauges (solid black line with grey shading indicating the estimated uncertainty) and using TOPEX/Poseidon/Jason‐1&2 satellite altimeter data (dashed black line). The two estimates have been matched at the start of the altimeter record in 1993. Also shown are the various contributing components. (b) The observed sea level and the sum of components. The estimated uncertainties are indicated by the shading. The two time series are plotted such that they have the same average over 1972 to 2008. From Church et al. (2011).

Looking into what we can expect for the impact of future sea level rise on hurricanes,Lin et al. (2012) found that:

"The combined effects of storm climatology change and a 1m [sea level rise] may cause the present NYC 100-yr surge flooding to occur every 3–20yr and the present 500-yr flooding to occur every 25–240yr by the end of the century."

So this human contribution to the Sandy-related damage is quite straightforward. This is what we know:

Humans increased the greenhouse effect.

The greenhouse effect caused the planet to warm.

The warming planet caused land ice to melt and the oceans to expand.

Melting land ice and thermal expansion caused average sea level to rise.

Higher sea level made the storm surge worse than it would have been in the past, thus causing more flooding.

Warmer Oceans Fuel Hurricanes

As Katharine Hayhoe noted, Atlantic sea surface temperatures (SSTs) are also significantly warmer than they were a century ago as a result of human-caused global warming. Figure 3 shows global surface temperature anomalies for the period 2000 to 2011 compared to 1900 to 1910. SSTs over most of the Atlantic ocean warmed 0.5 to 1.0°C over that timeframe.

MIT hurricane expert Kerry Emanuel first proposed in Emanuel (1987) that warmer SSTs should lead to stronger hurricanes. Emanuel (2005) confirmed that hurricanes have grown stronger over the past several decades, in part due to human-caused global warming. As he put it in Emanuel (2012),

"In the North Atlantic region, where tropical cyclone records are longer and generally of better quality than elsewhere, power dissipation by tropical cyclones is highly correlated with sea surface temperature during hurricane season in the regions where storms typically develop"

As a result, hurricane strength and damage are projected to increase in a warming world (Figure 4).

Figure 4: Accumulated damage from 2000 to the year on the x-axis using the the GFDL CM2.0 global climate model with climate held fixed at its 1981–2000 mean condition (blue) and under the global warming scenario associated with IPCC SRES Scenario A1B (red). The error bars shows one standard deviation up and down from the ensemble mean. From Emanuel (2012).

Elsner et al. and Knutson et al. (2010) also find that hurricanes will become stronger in a warming world.

"higher resolution modelling studies typically project substantial increases in the frequency of the most intense cyclones, and increases of the order of 20% in the precipitation rate within 100 km of the storm centre."

Again we have a very clear connection between human-caused global warming and impacts from Hurricane Sandy.

Humans increased the greenhouse effect.

The greenhouse effect caused the planet (including oceans) to warm.

Warmer oceans feed stronger hurricanes.

However, note that during the hurricane event, SSTs along the coast were approximately 3°C above average, whereas global warming has increased SSTs by closer to 0.6°C. Thus as Kevin Trenberth notes, while global warming contributed to the hurricane intensity, so did natural variability.

"With every degree F rise in temperatures, the atmosphere can hold 4 percent more moisture. Thus, Sandy was able to pull in more moisture, fueling a stronger storm and magnifying the amount of rainfall by as much as 5 to 10 percent compared with conditions more than 40 years ago. Heavy rainfall and widespread flooding are a consequence."

"recent trends in precipitable water are generally positive and, for 1988 through 2003, average 0.40±0.09 mm per decade or 1.3±0.3% per decade for the ocean as a whole"

We have another fairly simple causal relationship here:

Humans increased the greenhouse effect.

The greenhouse effect caused the planet (including atmosphere) to warm.

A warmer atmosphere can hold more water vapor.

This allows hurricanes to pull more moisture from the atmosphere.

More rainfall during the hurricane causes more widespread flooding.

Changing Weather Patterns Resulting from Arctic Warming

Francis and Vavrus (2012) found evidence that that the decline in Arctic sea ice and snow cover are linked to extreme weather, for example through more frequent blocking patterns. Liu et al. (2012) also found that "the decrease in autumn Arctic sea ice area is linked to changes in the winter Northern Hemisphere atmospheric circulation," which results in more frequent episodes of blocking patterns.

"While it’s impossible to say how this scenario might have unfolded if sea-ice had been as extensive as it was in the 1980s, the situation at hand is completely consistent with what I’d expect to see happen more often as a result of unabated warming and especially the amplification of that warming in the Arctic"

Extreme Weather on Steroids

The bottom line is that while global warming did not cause Hurricane Sandy, it did contribute to the "Frankenstorm" at least by causing higher sea levels (and thus bigger storm surges and flooding), warmer sea surface temperatures (and thus a stronger hurricane), and more moisture in the atmosphere (and thus more rainfall and flooding).

"There is no division, in the physical world, between “climate change storms” and “non-climate change storms.” Climate change is not an exogenous force acting on the atmosphere. There is only the atmosphere, changing. Everything that happens in a changed atmosphere is “caused” by the atmosphere, even if it’s within the range of historical variability."

Debating the extent to which Frankenstorm Sandy was put on steroids by climate change is a distraction.

Nearly all weather events now have a contribution from climate change and it is up to us to manage and reduce that risk with mitigative action."

We often come back to the words of Lonnie Thompson, who said that climate change will result in some mix of mitigation, adaption, and suffering. So far we have failed to achieve significant mitigation of greenhouse gas emissions, and as a result, extreme weather events on steroids like Hurricane Sandy will cause more suffering than they would otherwise have, and we will have to adapt to a future in which these types of events occur more frequently. Unfortunately, as we saw in North Carolina, some science-denying policymakers are not even willing to implement the necessary adaptation measures. This type of denial will maximize future suffering.

Imagine a world where this type of extreme weather event happens once per decade instead of once per century. That's one small part of what we're talking about when we discuss the impacts of climate change.

Comments

That quote from Roberts is very appropriate and accurate. In a couple of sentences it captures what many of us have being struggling to articulate clearly to the public. Hopefully he doesn't mind people borrowing it (with credit of course).

All the ocean to turn, and it was highly wind sheared on the approach to New Jersey, incredible how far it maintained hurricanes winds and a very low pressure, some of that accumulated deep water heat coming to the surface??

As everyone knows global warming didn't cause Sandy and the high lunar tide was very unfortuneate, but global warming as you said does seems to have been a helping hand in the impact path she took and does seem to have amplified her magnitude. For the end of October she was an unprecented storm in a long record of severe storms.

1:300 year event at least?

Following the USA drought and several other record rainfall events this year.

Global warming does seem to happening and some and in ways only now being fully recognised.

The diagnosis is serious extremes and new weather patterns.

And there is still another 0.6C warming to come, if not more considering the total lack of effective global action and the permafrost melting situation.

What is the next El Nino year going to bring!!!?

All natural factors have been tending to cooling recently, but we now entering a potential El nino period with a peak of sunspots combination next year.

Excellent article. Some of it puts into focus what I've been trying to tell a denier acquaintance. Mainly that the total energy of a storm says more than just wind speed, so storm size matters. But there is plenty of other information here. In far Western New York State, we got high winds and lots of rain, but not the type of destruction that the coastal regions received.

Thanks Dana, this is a nice summary. It reminds of something Aaron Lewis posted a bit ago at Tamino's site: The composition of the atmosphere affects the weather. All of the weather, all the time. We have changed the composition of the atmosphere. We are affecting the weather, all of the weather, all the time.

Personally, I think that really applies to storms and maybe heatwaves. When it comes to floods, the extra moisture in the atmosphere is enough in many cases (I'd speculate Brisbane/Queensland as a candidate) to tip the event over from manageable/not a flood at all to significant or catastrophic - entirely due to the warmed atmosphere.

"Sandy's barometric pressure at landfall was 946 mb, tying the Great Long Island Express Hurricane of 1938 as the most powerful storm ever to hit the Northeast U.S. north of Cape Hatteras, NC.

New York City experienced its worst hurricane since its founding in 1624, as Sandy's 9-foot storm surge rode in on top of a high tide to bring water levels to 13.88' at The Battery, smashing the record 11.2' water level recorded during the great hurricane of 1821."

Was also the biggest storm size area in Atlantic since they've been measured.

Fairly extreme event to break so many records, lets hope it is a unique event, for if another Hurricane even came close that would be mighty unual, but still possible under natural variation.

But this if this Hurricane is an indication of what Hurricanes are going to be more like (wetter, large but lower wind speed as so big) with warmer oceans and a changing climate, then the North East of American needs to start adaptating to the possibility of this being a more regular event.

"Changing Weather Patterns Resulting from Arctic Warming"
Yes. Look at the blocking high in forbidden territory, that is over de Cold Wall between Newfoundland and Greenland.
The persistence of this pattern is unique. Normally highs tend to exist there for maybe a day - in transit as an ending block the high moving into the Canadian Arctic (viz aroung 1 November 1985) or, more ordinary, as a transiting high moving to the Azores region.
The present blocking is highly, highly anomolous. And it has everything to do with Sandy's dramatic impact.

Climate science contrarians have often been criticized for conflating climate and weather, and try to turn the criticism about when climate science discusses the impact of climate on weather.

I recall seeing on the blog Deltoid a commenter waving away natural disasters with "it's just weather, innit?" as if to dispel the notion of the two being related.

Of course, it's not really the conflation of climate and weather that's the problem, it's the backwards attribution. When cold weather or snow was a "disproof" of climate change, contrarians were effectively claiming weather drives climate.

The impact of anthropogenic warming on Earth's ocean surface temperatures overall is measured at 0.6C. The surface temperature off the North American coast is measured at 3C.

Is there any work that can tease out the contribution of climate change on the coastal SSTs? My intuition tells me that it may not simply be that natural variation is responsible for 2.4C (additive). Would not the global forcing be like a gain, a multiplicative effect on natural variation?

Lambda: I just tried a very crude calc of temperatures in coastal cells vs all cells for HadSST3. There are differences in the resulting temperature record, but the warming since 1950 still looks like ~0.6C.

Pielke Jr. says in the Wall Street Journal today: "Humans do affect the climate system, and it is indeed important to take action on energy policy—but to connect energy policy and disasters makes little scientific or policy sense. There are no signs that human-caused climate change has increased the toll of recent disasters, as even the most recent extreme-event report of the Intergovernmental Panel on Climate Change finds. And even under the assumptions of the IPCC, changes to energy policies wouldn't have a discernible impact on future disasters for the better part of a century or more."

adelady, my ex was from the Woodford area: even in 'normal' flood events, the Stanley River would often flood, downstream of Somerset reservoir, to an extent that she was literally an island, unable to get to either Woodford or Kilcoy. she learned early on to lay in a stock of provisions and water. IIRC, Woodford is only about 40 clicks away from the coast.

Assuming flooding events might get more frequent there, that would put real kibosh on not only property values in that region, but its habitability. And that's just a *teensy* slice of an area that would be affected, just in Qld.

Tom @16 - this isn't the first time we've seen Pielke Jr.'s extreme weather obfuscation. If you boil it down, his argument is basically that we've been able to adapt to hurricane changes so far (i.e. better building engineering and better model predictions), therefore there's nothing to worry about. I'm not really sure how you adapt to New York being regularly underwater though.

Annoying, yes; but I posit we (rational, fact-based reserchers/scientists) only have a very limited window to 'trimtab' the conversation towards reality; as sure as, within a couple of weeks, folks exogenous to the 'Sandy zone' will tend to forget the enormity of it, and the MSM will, move onto the next "is the head dead yet?" meme.

This is an issue that we need to hammer on, to take a perfect opportunity (unfortunate to those who suffered through it, and will continue to do so) moment offered to us by Sandy, to counteract the superior (in its ability to "Tannoy" its disinforamtion) to a gullible populace.

This is indeed the tactic we need to utilize, and I believe we have had to use it for quite a long while, certainly since AR4 came out.

Pielke ignores that-- as with all adaptation-- accommodating ourselves to the mess we're creating will largely be an iterative process of mayhem at all scales. The larger a single destructive event, the fewer will successfully adapt.

Collectively we behave with little more intelligence than does evolution, as the very fact of continuing burgeoning C02 emissions concisely tells us.

Cases in point for illustration are photos of some portions of the New Jersey shoreline where the vague outlines of street grids can be seen below water, many yards out from a new shoreline. Those streets couldn't adapt quickly enough and they certainly were not planned intelligently.

In fig 1, could someone explain what explained the sea level rise in the early part of the 20th century (although it does appear that the trend line is slightly misleading, in that, the real rise only seems to have begun in the 1930s).

Is this just because of local factors (being Manhattan, there was probably some reclamation work being done in the early 20th century) or just random variation?

Addicted @24 - there was both global and local warming in the early 20th Century. I'd be more curious as to why local sea level rise continued during the mid-century 'cooling', though looking at local temp data, the mid-century cooling isn't easy to spot in the NY area.

Re: the BW article, Ive not checked yet but the mention of "climate deniers" in the *first* 'graph, of this *particular* publication, must be making spleens hemorrhage on WUWT et al, ad nauseum.

Appreciate the link and as I stated before, we in the rationalist camp have a huge job ahead and this gift of time (the silver lining of the dark cloud that is Sandy's dire effects) to reframe the conversdation is short.

I know it must be doing a little something, because some who I've contacted over the past few months are now asking me about this issue, in the new light in which it exists.

Keep up the unending and largely thankless job, SkSers! We've got a biosphere to save!

Dana @25 - Thanks for your response. Regarding your point about the lack of decline in the mid 20th century, as far as I can tell, local warming should not have made a difference to sea levels. Or am I wrong there?

Dana @25, the mid-century cooling is distinctly a NH phenomenon. Except for a slight blip coinciding with WW2, the SH warming has been continuous since 1920:

As most of the Earth's ocean surface lies in the Southern Hemisphere, SH temperatures would be a better predictor of sea level rise due to thermal expansion. SH temperatures would also be a better predictor of glacial retreat in the Andies, NZ and or course Antarctica as well.

Having said that, the rate of sea level did peak during the warm years of of the 30s and 40s, indicating that the NH roller coaster in temperature did have some impact.

Addicted @24, the recent sea level rise began about 1800, based on data from Jevrejevya:

The initial increase was due to the end of the Little Ice Age, brought about by a period with unusually few large equatorial volcanoes, a slight increase in solar radiation, and (almost certainly) a reduction in the Earth's albedo due to black carbon from the rapidly ongoing industrialization of Europe and America. (It must be remembered that in the 19th and early 20th century, trees in Europe and the NE US were so blackened with soot that the normal light form of the Peppered Moth was almost entirely replaced by the black form.)

However, the ongoing rise in sea temperatures is undoubtedly due to the onging rise in temperatures which is almost entirely due to anthropogenic factors.

Wow, that WSJ opinion piece by Pielke Jr. is quite the exercise in cherry picking and spin, not to mention ignoring inconvenient facts.

But I suppose one should not expect much from an opinion piece in the opinion pages of the WSJ, the same section that people like Lindzen and deniers have used to spread their ideology and pseudo-science. Roger Pielke Jr. is now playing the same game as the other contrarians and obfuscators and delayers who have exploited the very same opinion pages of the WSJ-- a paper that sadly seems only too happy to uncritically promulgate misinformation.

Ultimately it boils down to this, Roger Pielke Jr. is entitled to his misguided opinions, but he is not entitled to his own facts. In this case, as in many others, the facts do not agree with his (overvalued) opinion.

When asked by people I've been summing up the influence of climate change on Sandy with the following analogy.

It's like rain on the highway: it might not actually cause an accident but it 1) reduces visibility, 2) reduces grip, and 3) will likely mean that any accident that does occur will have a greater impact.

Well, RP JR has posted the WSJ editorial on his blog, along with a follow-up post, and unlike his dad, comments are open if anyone wants to pursue the generally fruitless diversion of rebutting him in the commetns ...

Pielke's the same fellow down on record claiming the head of the IPCC is corrupt. Pielke was wrong but I don't recall him public retracting his remark that Pachauri was guilty of "a classic and unambiguous case of financial conflict of interest."

Why would anybody listen to somebody so gullible as to repeat fabrications and also so sloppy as to not apologize when it turned out he was spreading slander? Is Pielke only imagining what he says in this op-ed? How are we to know, without diligently verifying his claims? If we have to double-check what Pielke says, of what use is he as a thought leader?

"However, note that during the hurricane event, SSTs along the coast were approximately 3°C above average, whereas global warming has increased SSTs by closer to 0.6°C. Thus as Kevin Trenberth notes, while global warming contributed to the hurricane intensity, so did natural variability".

And can't natural variability regionally amplify a forcing? That 0.6 C isn't exactly evenly distributed, and future warming won't be either. As the NERC/Met office/Royal society statement put it, "We expect some of the most significant impacts of climate change to occur when natural variability is exacerbated by long-term global warming, so that even small changes in global temperatures can produce damaging local and regional effects".

There's no need to claim that the whole SST anomaly was due to warming. Equally, there's no basis to claim that 0.6C was the warming ocean's only contribution. This should have been a teaching moment about averages. If the average warming is 0.6, then there must be, by definition, areas of water both above and below that average.

Therefore a good starting point for an area that is way, way over its 'normal' temperature for a specified period could be to consider that this particular part of the ocean is one of those above average areas.

But it's not a "classic and unambiguous case of financial conflict of interest" for Pat Michaels and some of the other climate change troglodytes to take money from the fossil fuel industry? I know it's been a tough week for them....too bad, they've earned it.

The sea level has been rising for over 7000 years and since 1400AD the sea coast of the NY Harbor (Barn Island,CN) has lowered my 100 CM. Less than 5% could be caused by human activity.
http://www.whoi.edu/science/GG/coastal/research/sealevel.html

Yet alarmist repeatedly decree its all manmade activity and the end of civilzation is near unless we ALL do somthing drastic.

GordonD - I'm afraid that the sea level has not been rising for 7000 years. And current rise at many times recent historic rates is entirely due to global warming, driven primarily by anthropogenic factors. You are not supporting your argument with your first link, incidentally, which notes recent high rates of sea level rise - and says nothing about attribution.

I suggest you take a look at Jerry Mitrovica's video - he shows rates of sea level rise over the last few millennia quite clearly. Pay attention to the Roman fishtanks, coral heads, and dates for solar eclipses as direct evidence.

---

Sandy may or may not have occurred without global warming. However, the quite warm sea surface temperatures and higher total humidity made it stronger, and the blocking patterns driven by Arctic warming directed it to our coast - without global warming Sandy could not have been so damaging.

KR - A lot of commenters get confused over the global sea level trend, and the trend around areas such as the eastern coast of the US, which was uplifted by the presence of the gigantic Laurentide ice sheet during the last ice age, and which has subsided ever since the ice sheet began to disintegrate. The US is still slowly sinking even though the ice sheet has long disappeared.

Therefore the two trends will be somewhat different. Gordon's confusion probably runs a bit deeper than that though.

Thank you for the Link to Dr Mitrovica Video, it had some very good theories. His off hand comment that coral 3M above the water was proof enough of no rise in pre-recorded history, is not backed with any studies. This is a classic fitting of observations to a theory, and not forming a theory from the data. In the video he says never to use tide guages near 'faults' But yet the area of italy/grease the fish tanks are in, are known for volcanic upheaval. He did not mention when the tanks were built, but late roman era would be 200AD? Less than 2000 years of rising IN THE mederterianian may be less than significant. [SNIP]

As far seas not rising, as I understand it, the last major Ice age the glaciers were south of Ohio and very thick. Over the past 30,000 years the ice has melted. If the Sea level did not rise, where did all that water go? Maybe the Woods Hole studies are all wrong, and 95% of the rising happened in just the past 100 years? But I have my doubts.

For the record, I belive the climate is changing, and has always been changing, and the change in rate maybe anthropogenic in nature. The strengh of storms are effected by the heat of the air and oceans. But the media pushes activist theories that mankind is the sole cause and we need to stop the global climate change (as if we could), and at what lost oppurtunity costs.

Anyways, I will keep my mind open about climatology theories. Please keep your own minds open about mans effects on the world, is no greater than the worlds effect on man. Thank you and Good bye.

@40 Dana, I value your posts and work highly, but simply liking to a blog which states something that cannot be verified is not 'a source'. If I would trust that level of information then I could simply go to WUWT for my daily climate info. I expect SkSc to do better.

"Maybe the Woods Hole studies are all wrong, and 95% of the rising happened in just the past 100 years?"

No. You just fail to understand why the sea level trend in a subsiding region of the world is different to the global average. Relative sea level, i.e what would be observed in a subsiding region, will rise even when the global ocean volume is unchanging. This is because the land is sinking.

When global ocean volume began to increase, as it did after the Industrial Revolution, then the rate of sea level rise off the eastern coast of the USA increased further again.

It seems to me that this post contradicts the latest IPCC report on extreme events, SREX, published in March 2012, where it says:

"There is low confidence in any observed long-term (i.e., 40 years or more) increases in tropical cyclone activity (i.e., intensity, frequency, duration), after accounting for past changes in observing capabilities."

Obviously this was written before Sandy, but as you know, "weather is not climate".

Also, I checked but didn't find the source for the claim of "record breaking pressure" on the link given.
There is another link in the linked page, which points to a different post, stating that the Sandy's low pressure is tied up with that of Great Long Island Express Hurricane of 1938.